A touchscreen is an input device normally layered on the top of an electronic visual display of an information processing system. The touchscreen enables the user to interact directly with what is displayed, rather than using a mouse, touchpad, or any other intermediate device. Generally, a user can give input or control the information processing system through simple or multi-touch gestures by touching the screen with a special stylus/pen and-or one or more fingers. Some touchscreens require ordinary or specially coated gloves to work while others use a special stylus/pen only. The user can employ the touchscreen to react to what is displayed and to control how it is displayed—for example, zooming to increase the text size.
Touchscreens generally use either resistive or capacitive technology to sense touch. A resistive technology-based touchscreen typically employs two transparent electrically-resistive layers separated by a thin gap. A voltage is applied to one of the two layers. When a top layer is touched, it deflects and locally connects with the lower layer, thus permitting the lower layer to detect the touch. The capacitive technology is based on capacitive coupling that uses human body capacitance as input. Capacitive sensors detect anything that is conductive or has a dielectric that is distinct from air. A capacitive touchscreen panel typically consists of an insulator such as glass, coated with a transparent conductor such as indium tin oxide (InSnO) or ITO. As the human body is also an electrical conductor, touching the surface of the screen results in a distortion of the screen's electrostatic field, measurable as a change in capacitance. Different technologies may be used to determine the location of the touch, which is then communicated to a controller for processing.
Touchscreens are common in devices such as game consoles, personal computers, tablet computers, electronic voting machines, and smartphones. Touchscreens can also be attached to computers or, as terminals, to networks. Touchscreens also play a prominent role in the design of digital appliances such as personal digital assistants (PDAs) and some books (E-books). Contemporary vehicles also use touchscreens to provide user interface with the vehicles' infotainment systems. Touchscreens typically use flat panel liquid-crystal displays (LCDs) for the light modulating properties of liquid crystals.